Cellular streptolysin S-related hemolysins of group A Streptococcus C203S

The role of iron in the growth and hemolysin (Streptolysin S) production in Streptococcus pyogenes

Four strains of Streptococcus pyogenes were propagated at 37 degrees C in a reduced iron medium supplemented with Fe3+-citrate to give concentrations of 1 through 11 micrograms per milliliter, in order to observe the effects of iron on growth and on the vitro production of Streptolysin S. Both growth and hemolysin production were observed to be influenced by medium iron concentration of which 1.2 micrograms per ml of iron was critical. Hemolysin was produced during the exponential phase of the growth cycle with maximum yield as the organism entered the stationary phase. Hemolytic activity (which was accepted as the ability of the hemolysin to lyse sheep erythrocytes) fell below detectable levels as the organisms entered fully into the stationary phase (9-10 hours post incubation). Serum (bovine, human, chicken) was observed to have a high stabilizing effect on the hemolysin.

The role of protease in streptolysin S formation

Production of streptolysin S by streptococci was found to be inhibited by treatment with protease inhibitors, tosylphenylalanine chloromethyl ketone (TPCK), tosyllysine chloromethyl ketone (TLCK), or phenylmethylsulfonyl fluoride (PMSF), even in the presence of the inducer oligonucleotides. Other protease inhibitors, antipain, leupeptin, or pepstatin were found to have little or no effect. Trypsin reversed the effect of TPCK or TLCK. The reversal was dependent upon the amount of added trypsin and the incubation time at 37 degrees C, suggesting that a protease activity was involved in the hemolysin formation. The effect of trypsin was not observed if chloramphenicol was also added, suggesting that a precursor of streptolysin S was processed as it was synthesized and released into medium as the active hemolysin, by the concerted action of a protease and inducer oligonucleotides. Experiments with the subcellular fractions of streptococci indicated that the streptolysin precursor was localized in the insoluble fraction and the "processing" protease in the supernatant fraction.

Streptolysin S activation by lipoteichoic acid

Lipoteichoic acid from streptococci and Staphylococcus aureus both activated membrane-bound precursor streptolysin S and induced the formation of extracellular streptolysin S. Lipoteichoic acid could replace other substances, such as yeast ribonucleic acid core, that act as carriers for hemolysin but which are not components of the streptococcus or the host. Lipoteichoic acid may play a role as the physiological carrier of streptolysin S to host tissues.

Membrane and cytoplasmic location of streptolysin S precursor

Group A streptococci which produce streptolysin S (SLS) contain a cellular potential hemolysin (CPH) which is precursor to extracellular SLS. Since the cellular location of CPH is unknown, protoplasts prepared with group C phage-associated lysin or mutanolysin from 18 strains of group A streptococci were fractionated into subcellular components and assayed for CPH. In all strains, most of the CPH was membrane associated, and most could not be removed from membranes by washing with buffer or 2 M LiCl. CPH remaining in the cytoplasmic fraction was sedimentable, but not associated with membrane fragments. Ribonuclease digestion neither solubilized nor inactivated CPH from membranes. Streptococcal proteinase also did not affect CPH, although it did inactivate SLS. We conclude that group A streptococci contain a major pool of CPH in the membrane and a smaller pool in the cytoplasm.

Properties of a hemolysin produced by group B streptococci

A hemolysin that appears to be responsible for the zones of beta-hemolysis surrounding colonies of group B streptococci (Streptococcus agalactiae) on blood agar plates has been isolated and partially purified. No soluble hemolysin was detectable in the supernatants of streptococcal cultures grown in several types of media. However, hemolytic activity was detected when streptococci were incubated with erythrocytes, and soluble hemolysin was isolated when bacterial suspensions were incubated in the presence of a variety of agents, including calf serum, albumin, Tween 80, and starch. Glucose and other fermentable carbohydrates stimulated hemolysin production, and metabolic inhibitors greatly reduced the titer of hemolysin that could be recovered, suggesting that cellular metabolism is necessary for hemolysin production or release. The soluble hemolysin was concentrated by ammonium sulfate precipitation and partially purified by gel filtration. Agents known to inhibit other streptococcal hemolysins, including phospholipids, trypan blue, proteases, and cholesterol, were tested for their effect on the group B hemolysin. Only the phospholipids inhibited hemolysin activity. The group B streptococcal hemolysin appears to be similar to, but distinct from, streptolysin S produced by Streptococcus pyogenes.

Effect of detergents on streptolysin S precursor

Group A streptococci which produce streptolysin S contain a cellular precursor to streptolysin S in the membranes and cytoplasm which is activatable by blending in a Vortex mixer with glass beads and ribonucleic acid (RNA)-core (RNA preparation from yeast). Although no activation of precursor occurred when it was mixed with detergents, it was activated when blended with glass beads and detergents such as Tergitol NP-40 and Brij 35. Maximum activation of precursor was achieved in 1 to 2% detergent, in pH 6.5 buffer, and after 8 min of blending. Detergents Tween 20, 40, 60, and 80, Brij 56, and Lubrol WX also activated precursor, but, of all the hemolysin preparations, those with Tween 40 or 60 or Lubrol WX were the most stable. The addition of RNA-core during or after blending of precursor with detergents enhanced the titer and stability of the hemolysin. This was due in part to the association of the hemolytic moiety with RNA-core. Activation of precursor in the membrane was better with a detergent, whereas that in the cytoplasm was better with RNA-core. Therefore, precursor from two different cellular locations can be differentiated by the effects of RNA-core and detergents on precursor titer.

Activation of streptolysin S-related cellular potential hemolysin by grinding with glass beads

Cellular potential hemolysin, the precursor to extracellular streptolysin S, was activated by grinding with glass beads on a Vortex mixer. Hemolysin activity was markedly enhanced by the addition of ribonucleic acid-core during the grinding. Determinants for optimum results with the beads included small bead size, prewashing of beads with acetic acid, and appropriate bead volume during grinding. The increased sensitivity of this technique over those previously used revealed cellular potential hemolysin in cells grown in the presence of glucose, which inhibits streptolysin S production. The basis for the increased sensitivity of this procedure may be due to the binding of cellular potential hemolysin or ribonucleic acid to the beads.

Lysis and protoplast formation of group B streptococci by mutanolysin

Group B streptococci, refractory to previously tested muralysins under physiological conditions, were successfully converted to protoplasts by use of a recently describede N-acetyl muramidase, mutanolysin, derived from a streptomycete. Purified enzyme was effective, but crude preparations, although degrading cell walls, simultaneously produced peculiar effects of cytoplasmic coagulation, retention of cell shape, loss of some intracellular enzymes, and a rise in optical density. Addition of purified mutanolysin to the array of muralysins (group C streptococcal phage-associated lysin, lysozyme), previously successful in preparing protoplasts of different streptococci, now makes possible enzymatic preparation of protoplasts of streptococci of groups A, B, C. D. G, and H.

Repression of heat-stable enterotoxin synthesis in enterotoxigenic Escherichia coli

Five different carbon sources were examined for their ability to control synthesis of heat-stable enterotoxin (ST) by enterotoxigenic (ENT+) Escherichia coli grown in either a defined medium containing four amino acids or a minimal salts medium. No ST activity was observed when D-glucose, D-gluconate, and L-arabinose were added separately to the defined medium, whereas glycerol and pyruvate decreased toxin levels. Similar results were obtained using a minimal salts medium, except with pyruvate, which did not support growth. Inhibition of ST synthesis by D-glucose was overcome by the addition of 3 X 10(-3) M cyclic adenosine 3',5'-monophosphate. Glucose repression of beta-galactosidase synthesis under conditions optimal for inhibition of ST synthesis was also reversed by exogenous cyclic adenosine 3',5'-monophosphate in the presence of the inducer isopropyl-beta-D-thiogalactopyranoside. The data suggest that control mechanisms for the synthesis of plasmid gene products of bacterial pathogens are similar to those exerted on the host chromosome.

Relationship of cellular potential hemolysin in group A streptococci to extracellular streptolysin S

The relationship of streptolysin S (SLS) and a cellular potential hemolysin (PH) activatable by sonication was examined in strain C203S (a known high producer of SLS), its SLS(-) mutant (C203U), and in 20 other group A streptococci of various M and T serotypes. All strains shown to form SLS (ribobycleic acid (RNA)-core SLS) contained PH. The two strains lacking PH were the only ones that did not produce SLS In strain C203S, formation of SLS bycells incubated with RNA-core for 60 min at 47 C in a nongrowth basal medium (Bernheimer's basal medium) was followed by a marked decrease (99.6% loss) of PH titer. Without stimulation of SLS production by addition of RNA-sore, the same incubation resulted in a progressive but less marked fall (38.8%loss in 60 min) of PH titer: these cells produced disproportionately low titers of SLS on subsequent addition of RNA-core. This effect of prior incubation in Bernheimer's basal medium on SLS titer was partially nullified by use of fresh medium after 30 min, but not after 60 min, and did not occur during 60 min of incubation at OC. These results provide additional evidence for a precursor-product relationship between PH and SLS. They also suggest that a medium factor (or factors) is utilized or destroyed at 37 C and that this factor is essential to both the stability of PH and its efficient conversion to SLS.

Cellular location of streptolysin O

Streptolysin O was measured in subcellular fractions of group A streptococci obtained after preparation of protoplasts in a hypertonic buffer containing raffinose. Most of the activity was located in the periplasm (the region between cell wall and membrane) and did not differ in several characteristics from that of extracellular streptolysin O. Of the enzymes used as subcellular markers, aldolase and maltase (cytoplasmic) and acid phosphatase (membrane associated) were in the same fractions as found in other bacteria. However, the location of alkaline phosphatase differed from that of other bacteria in the most of the activity was in cytoplasm rather than in the periplasm.